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62
Crossing Over the Bounded Domain: From Exponential to Powerlaw Intermeeting Time in MANET
, 2007
"... Intermeeting time between mobile nodes is one of the key metrics in a Mobile Adhoc Network (MANET) and central to the endtoend delay and forwarding algorithms. It is typically assumed to be exponentially distributed in many performance studies of MANET or numerically shown to be exponentially di ..."
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Cited by 77 (5 self)
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Intermeeting time between mobile nodes is one of the key metrics in a Mobile Adhoc Network (MANET) and central to the endtoend delay and forwarding algorithms. It is typically assumed to be exponentially distributed in many performance studies of MANET or numerically shown to be exponentially distributed under most existing mobility models in the literature. However, recent empirical results show otherwise: the intermeeting time distribution in fact follows a powerlaw. This outright discrepancy potentially undermines our understanding of the performance tradeoffs in MANET obtained under the exponential distribution of the intermeeting time, and thus calls for further study on the powerlaw intermeeting time including its fundamental cause, mobility modeling, and its effect. In this paper, we rigorously prove that a finite domain, on which most of the current mobility models are defined, plays an important role in creating the exponential tail of the intermeeting time. We also prove that by simply removing the boundary in a simple twodimensional isotropic random walk model, we are able to obtain the empirically observed powerlaw decay of the intermeeting time. We then discuss the relationship between the size of the boundary and the relevant timescale of the network scenario under consideration. Our results thus provide guidelines on the design of new mobility models with powerlaw intermeeting time distribution, new protocols including packet forwarding algorithms, as well as their performance analysis.
Balancing traffic load in wireless networks with curveball routing
 IN: PROC. ACM MOBIHOC.
, 2007
"... We address the problem of balancing the traffic load in multihop wireless networks. We consider a pointtopoint communicating network with a uniform distribution of sourcesink pairs. When routing along shortest paths, the nodes that are centrally located forward a disproportionate amount of traff ..."
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Cited by 40 (0 self)
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We address the problem of balancing the traffic load in multihop wireless networks. We consider a pointtopoint communicating network with a uniform distribution of sourcesink pairs. When routing along shortest paths, the nodes that are centrally located forward a disproportionate amount of traffic. This translates into increased congestion and energy consumption. However, the maximum load can be decreased if the packets follow curved paths. We show that the optimum such routing scheme can be expressed in terms of geometric optics and computed by linear programming. We then propose a practical solution, which we call Curveball Routing that achieves results not much worse than the optimum. We evaluate our solution at three levels of fidelity: a Java highlevel simulator, the ns2 simulator, and the Intel Mirage Sensor Network Testbed. Simulation results using the highlevel simulator show that our solution successfully avoids the crowded center of the network, and reduces the maximum load by up to 40%. At the same time, the increase of the expected path length is small, i.e., only 8 % on average. Simulation results using the ns2 simulator show that our solution can increase throughput on moderately loaded networks by up to 15%, while testbed results show a reduction in peak message load by up to 25%. Our prototype suggests that our solution is easily deployable.
Random waypoint mobility model in cellular networks,” Wireless Networks
, 2007
"... Abstract. In this paper we study the socalled random waypoint (RWP) mobility model in the context of cellular networks. In the RWP model the nodes, i.e., mobile users, move along a zigzag path consisting of straight legs from one waypoint to the next. Each waypoint is assumed to be drawn from the u ..."
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Cited by 21 (4 self)
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Abstract. In this paper we study the socalled random waypoint (RWP) mobility model in the context of cellular networks. In the RWP model the nodes, i.e., mobile users, move along a zigzag path consisting of straight legs from one waypoint to the next. Each waypoint is assumed to be drawn from the uniform distribution over the given convex domain. In this paper we characterise the key performance measures, mean handover rate and mean sojourn time from the point of view of an arbitrary cell, as well as the mean handover rate in the network. To this end, we present an exact analytical formula for the mean arrival rate across an arbitrary curve. This result together with the pdf of the node location, allows us to compute all other interesting measures. The results are illustrated by several numerical examples. For instance, as a straightforward application of these results one can easily adjust the model parameters in a simulation so that the scenario matches well with, e.g., the measured sojourn times in a cell.
On Traffic Load Distribution and Load Balancing in Dense Wireless Multihop Networks
 EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING
, 2007
"... We study the load balancing problem in a dense wireless multihop network, where a typical path consists of a large number of hops, that is, the spatial scales of a typical distance between source and destination and mean distance between the neighboring nodes are strongly separated. In this limit, w ..."
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Cited by 17 (4 self)
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We study the load balancing problem in a dense wireless multihop network, where a typical path consists of a large number of hops, that is, the spatial scales of a typical distance between source and destination and mean distance between the neighboring nodes are strongly separated. In this limit, we present a general framework for analyzing the traffic load resulting from a given set of paths and traffic demands. We formulate the load balancing problem as a minmax problem and give two lower bounds for the achievable minimal maximum traffic load. The framework is illustrated by considering the load balancing problem of uniformly distributed traffic demands in a unit disk. For this special case, we derive efficient expressions for computing the resulting traffic load for a given set of paths. By using these expressions, we are able to optimize a parameterized set of paths yielding a particularly flat traffic load distribution which decreases the maximum traffic load in the network by 40 % in comparison with the shortestpath routing. Copyright © 2007 E. Hyytiä and J. Virtamo. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1.
Interference and Outage in Mobile Random Networks: Expectation, Distribution, and Correlation
"... In mobile networks, distance variations caused by node mobility generate fluctuations in the channel gains. Such fluctuations can be treated as another type of fading besides multipath effects. In this paper, the interference statistics in mobile random networks are characterized by incorporating ..."
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Cited by 12 (2 self)
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In mobile networks, distance variations caused by node mobility generate fluctuations in the channel gains. Such fluctuations can be treated as another type of fading besides multipath effects. In this paper, the interference statistics in mobile random networks are characterized by incorporating the distance variations of mobile nodes to the channel gain fluctuations. The mean interference is calculated at the origin and at the border of a finite mobile network. The network performance is evaluated in terms of the outage probability. Compared to a static network, the interference in a single snapshot does not change under uniform mobility models. However, random waypoint mobility increases (decreases) the interference at the origin (at the border). Furthermore, due to the correlation of the node locations, the interference and outage are temporally and spatially correlated. We quantify the temporal correlation of the interference and outage in mobile Poisson networks in terms of the correlation coefficient and conditional outage probability, respectively. The results show that it is essential that routing, MAC, and retransmission schemes need to be smart (i.e,. correlationaware) to avoid bursts of transmission failures.
Stochastic Properties of Mobility Models in Mobile Ad Hoc Networks
"... The stochastic model assumed to govern the mobility of nodes in a mobile ad hoc network have been shown to significantly affect the network’s coverage, maximum throughput, and achievable throughputdelay tradeoffs. In this paper, we compare several mobility models, including the random walk, random ..."
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Cited by 7 (0 self)
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The stochastic model assumed to govern the mobility of nodes in a mobile ad hoc network have been shown to significantly affect the network’s coverage, maximum throughput, and achievable throughputdelay tradeoffs. In this paper, we compare several mobility models, including the random walk, random waypoint and Manhattan models, on the basis of the number of states visited in a fixed time, the time to visit every state in a region, and the effect of the number of wandering nodes on the time to first entrance to a set of states. These metrics for a mobility model are useful for assessing the achievable event detection rates in surveillance applications where wirelesssensorequipped vehicles are used to detect events of interest in a city. We also consider mobility models based on Correlated Random Walks, which can account for time dependency, geographical restrictions, and nonzero drift. We demonstrate that these models are analytically tractable by using a matrixanalytic approach to derive new, closedform results in both the time and transformdomains for the probability that a node is at any location at any time for both semiinfinite and finite onedimensional lattices. We also derive first entrance time distributions for these walks. We find that a correlated random walk (i) covers more ground in a given amount of time and takes a smaller amount of time to cover an area completely than a random walk with the same average transition rate; (ii) has a smaller first entrance time to small sets of states than the random waypoint and random walk models and (iii) leads to a uniform distribution of nodes (except at the boundaries) in steady state. Index Terms MANET, mobility models, correlated random walk, random walk, random waypoint model.
A smoothturn mobility model for airborne networks
 in Proc. 1st ACM MobiHoc Workshop Airborne Netw. Commun
, 2012
"... Abstract—The design of effective routing protocols in airborne networks (ANs) relies on suitable mobility models that capture the movement patterns of airborne vehicles. As airborne vehicles cannot make sharp turns as easily as ground vehicles do, the widely used groundbased mobile ad hoc network ..."
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Cited by 7 (4 self)
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Abstract—The design of effective routing protocols in airborne networks (ANs) relies on suitable mobility models that capture the movement patterns of airborne vehicles. As airborne vehicles cannot make sharp turns as easily as ground vehicles do, the widely used groundbased mobile ad hoc network (MANET) mobility models are not appropriate to use as the analytical frameworks for airborne networking. In this paper, we introduce a novel mobility model, which is called the smoothturn (ST) mobility model, that captures the correlation of acceleration of airborne vehicles across temporal and spatial coordinates. The proposed model is realistic in capturing the tendency of airborne vehicles toward making straight trajectories and STs with large radii, yet is tractable enough for analysis and design. We first describe the mathematics of this model and then prove that the stationary node distribution is uniform. Furthermore, we introduce a metric to quantify the degree of model randomness, and using this, we compare and classify several mobility models in the literature. We conclude this paper with several possible variations to the basic ST mobility model. Index Terms—Airborne networks, mobility models, randomness. I.
Mobility Modeling and Performance Evaluation of Heterogeneous Wireless Networks
"... Abstract—The futuregeneration wireless systems will combine heterogeneous wireless access technologies to provide mobile users with seamless access to a diverse set of applications and services. The heterogeneity in this intertechnology roaming paradigm magnifies the mobility impact on system perf ..."
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Cited by 6 (3 self)
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Abstract—The futuregeneration wireless systems will combine heterogeneous wireless access technologies to provide mobile users with seamless access to a diverse set of applications and services. The heterogeneity in this intertechnology roaming paradigm magnifies the mobility impact on system performance and user perceived service quality, necessitating novel mobility modeling and analysis approaches for performance evaluation. In this paper, we present and compare three mobility models in twotier integrated heterogeneous wireless systems, the independence model as a naive extension of the traditional cell residence time modeling techniques for homogeneous cellular networks, the basic Coxian model which takes into consideration the correlation between the residence time within different access technologies, and the extendedCoxian model for further improved estimation accuracy. We propose a general stochastic performance analysis
G.: A Mobility Model for Pedestrian Content Distribution
 In: SIMUTools 2009: Proceedings of the 2nd International Conference on Simulation Tools and Techniques
, 2009
"... Mobile communication devices may be used for spreading multimedia data without support of an infrastructure. Such a scheme, where the data is carried by people walking around and relayed from device to device by means of short range radio, could potentially form a public content distribution system ..."
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Cited by 6 (3 self)
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Mobile communication devices may be used for spreading multimedia data without support of an infrastructure. Such a scheme, where the data is carried by people walking around and relayed from device to device by means of short range radio, could potentially form a public content distribution system that spans vast urban areas. The transport mechanism is the flow of people and it can be studied but not engineered. The question addressed in this paper is how well pedestrian content distribution may work. We answer this question by modeling the mobility of people moving around in a city, constrained by a given topology. Our contributions are both the queuing analytic model that captures the flow of people and the results on the feasibility of pedestrian content distribution. Furthermore, we discuss possible extensions to the mobility model to capture speeddistance relations that emerge in dense crowds.
Random Waypoint Model in nDimensional Space
 OPERATIONS RESEARCH LETTERS
, 2005
"... The random waypoint model (RWP) is one of the most widely used mobility models in performance analysis of mobile wireless networks. In this paper we extend the previous work by deriving an analytical formula for the stationary distribution of a node moving according to a RWP model in ndimensional s ..."
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Cited by 5 (1 self)
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The random waypoint model (RWP) is one of the most widely used mobility models in performance analysis of mobile wireless networks. In this paper we extend the previous work by deriving an analytical formula for the stationary distribution of a node moving according to a RWP model in ndimensional space.